The shattered remains of a reactor building loom against a lowering sky, smoke or steam pouring from a gaping roof in the days after a huge tsunami smashed into Japan, crushing a nuclear power plant.

This is just one of the more than 2,000 previously unseen images released by Fukushima operator Tokyo Electric Power showing the period between March 15, 2011, just four days after the tsunami struck, and April 11.

In some, a brochure blue sky glints with spring sunshine, giving no hint of the radioactive particles being pumped into it from the crippled reactors, sent into meltdown when cooling systems failed.

The pictures show fragments of plant machinery, vehicles and power station detritus mixed together in the swirling waters and dumped when the sea retreated.

It was into an air heavy with the stench of industrial oils and rotting sea life left behind that workers rushed as they battled to contain the world's worst nuclear disaster for a generation.

The photographs show the rudimentary conditions they had to deal with as they battled to cool reactors; the power lines downed, tankers over-turned and metal good only for scrap lying everywhere.

Almost two years since the disaster, the reactor units are now under control, but the clean up is far from complete.

Tens of thousands of people remain displaced, unable to return to their homes in the shadow of the power plant.

Scientists warn it could take 40 years to make some parts of the area safe again; others may never be habitable.

The tsunami claimed around 19,000 lives and destroyed swathes of northeast Japan. No one is officially recorded as having died as a direct result of the nuclear disaster.